An along-the-channel model is developed for evaluating the effects of various design and operating parameters on the performance of a proton exchange membrane (PEM) fuel cell. The model, which is based on a previous one, has been extended to include the convective water transport across the membrane by a pressure gradient, temperature distribution in the solid phase along the flow channel, and heat removal by natural convection and coflow and counterflow heat exchangers. Results from the model show that the performance of a PEM fuel cell could be improved by anode humidification and positive differential pressure between the cathode and anode to increase the back transport rate of water across the membrane. Results also show that effective heat removal is necessary for preventing excessive temperature which could lead to local membrane dehydration. For heat removal and distribution, the counterflow heat exchanger is most effective.